Differential A-to-I editing of SINE B2 RNAs unveils an epitranscriptome response to Aβ neurotoxicity.

Adenosine-to-inosine (A-to-I) RNA editing is a major epitranscriptomic mechanism, yet its contribution to non-coding RNA regulation during neurodegeneration is largely unknown. SINE B2 RNAs represent the dominant editing substrates in mice and have been shown to regulate gene expression. Here, we introduce and validate a repeat-aware bioinformatics framework that enables position-specific quantification of A-to-I editing within SINE RNAs, which has been challenging using standard genome-based pipelines. Applying this approach, we identify discrete editing hotspots in mouse SINE B2 RNAs that are selectively increased during early amyloid beta pathology in independent mouse models and in hippocampal neurons exposed to amyloid beta toxicity. Functional perturbation of ADAR activity alters both B2 RNA editing levels and the expression of B2 RNA-regulated genes, directly linking RNA editing to SINE-mediated transcriptional control. Nanopore sequencing confirmed increased RNA modification signals at these regions. Together, our findings establish a previously unrecognized epitranscriptomic response to amyloid beta neurotoxicity mediated by site-specific A-to-I editing of SINE RNAs.